Composition roofing



Dec' 6, 1949' H. w. GREIDER ET AL 2,490,430

COMPOSITION ROOFING Filed Aug. 7, 1945 2 sheets-sheet 2 Patented Dec. 6, 1949 UNITED STATES PATENT 10F-FICE 'Fasold, -Mount Healthy, Ohio, assgnors 'toThe Philip Carey Manufacturing Company, -a oorporation ofOh-io .Application August 7, 1943Se1fal No.497g80 14 Claims.

YThis invention relates to roofing. It relates particularlyi'to roong embodying bituminous material as waterproong.

Heretofore bituminous prepared roofing `has been `very extensively manufactured using as a base -a brous web such as roofingtelt, impregnating the "fibrous 4web Vwith la bituminous 'material, and coating the impregnated -web with a weather-resistant bituminous 'coating composition. The bituminous coating composition lusually contains a 'mineral 'filler such as slate iiour or `4powdered limestone in amounts --less l`than :about 40% Yby weight Jof the 'bituminous coating composition. Usually 'there is'appli'ed to the `bituminous 'coating on -the surface intended 'to be 'exposed to the weather a vsuitable :granular `materialsuch vars/slate granules or `more Liinel-y-divided 'mineral 'surfacing materialsuch as talc or mica. Finely-divided materials suchas mica akes, talc, silica dust or the like may be made adherent Yto 'the 4non-weather 'exposed surface of Kthe -roong to prevent'stickingof adjacent layers'of kthe roofing material in the package.

The 'termroongis1used'herein in the 'broad sense as referring -to -waterand 'weather-resistvant coverings Lsuch as shingles (individual or strip Ishingles), roo`ng tiles, l'cap sheets, base sheets, sidingS, roof `"deck coverings made from such `preformed materials, 'built-up molines, and the like.

The bituminous-roofings'of-the vcharacter aforesaid that-'have been'manufactured yand sold heretofore rhave 'relatively -low re resistance. lThe most widely 'accepted tests for determining the fire-resistant properties of roofing are'those vprescribed -by Underwriters Laboratories, Inc., of Chicago, Illinois. According to the Vtests prelscribe'dby Underwriters Laboratories, lInc., fireretardant `frootlngs Y are fplaced iin `three classifications, depending upon their ability "to pass the :tests #requiredf'forf such classification; Athese classi- .'cations'being-classA,class --Bfand class C. The class fC rating iis fthe lowest 'hre-retardant rating Aand f serves fte-distinguish Toolings having appreciable lire-,retardant properties from `roofingslhaving littlefor no fire-retardant `properties such. asfuntreated wood shingleswlr1ichI of. course, are :readily lvignited Sand ten'd to vburn Yfreely. So far as we are-aware, prepared bituminous rootings nf :the type iheretofore `:on vthe market mad-e onta felt base'of Aorganiciarlloer Vhave -notbeeniable tofattain, :regardlessxof tthe thickness thereof yor the inuniloer fof thicknesses, a :rating .of -Underwritersflliaboratoriesglnc.rhigherithan anlass C rating. The class A rating is the highesttrating awarded by Underwriters Laboratories, Inc., .and is reservedpior such Ahighly ,nre-retardant rool'inss lasbestos-cenient,shingles of the double .coverage type. Class B I`is an intermediate rating 5 and iis, for example, awarded to rooiingssuch as single coverage asbestos-cementsliingles. Abrief description of -the class A, class B and class "C ,fire-retardant tests- ,of Underwriters Laboratories, Inc. is contained 'in our pending applicaber 18,'1'940 (Patent No. 2 ;326,'723) andSenNo. 399,024,.led,June'20,`19;41 ,(Patent No. 2,326,724)

'It isapurpo'se of 'this invention to improve the re resistance of roongs comprising a layer of '15 thermoplastic materialsuc'h as bituminous mate- 20 the cos't of ordinary bituminous roong material,

that is so `highly''fire-retarda'nt that va threelaver covering O n a combustible Vroof deck will satisfactorily withstand exposure to the class A fire-retardant tests prescribed "by Underwriters 125 Laboratories, Inc. `We *have found ,further that such roong Vmaterial embodying our invention, when applied so ,as to provide ,two layers, will satisfactorily 4pass the class "B lire-retardant tests prescribed "by Underwriters Laboratories,

(30 IDC.

The'importa'nce of fire-resistant properties for roong is self-evident. 'Certain roofings such as asbestos-cement shingles, tile and the like :have high 'fire resistance but such roongs are Very ,1,35 costlyas 'compared'with asphalt-felt rooiingsand 'for this `reason asphalt-felt roongs are very extensively 'used 'on all 'kinds of structures notwithstanding ithe 'limited "fire `protection that is afforded by this Atype of frooiing. According Ato 40 this invention,asphalt felt Yroongs can be made without 'substantial increase in cost which are comparableinre-retardant properties to relatively much Imore `costly -roong constructions such as la'sloestos-cement,-tilel andthe like.

f4 5 v`Substantially all Jbituminous roongs comprise a strain-resisting base or foundation vsheet such as roong ifelt which is, coated with a bituminous coating that fprovides waterprooiing and weather resistance. This invention 'has itodo with ithe 50 coating fmaterial arather `-than Ythe lbase sheet.

While fthe ibase-sheet Imight be made of vnonconibustible material, the non-'combustibility of .the :base sheetl :does :not :solve .fthe a problem -zif the bituminous i coating itself ibnrns. Vor tends to Vow :55 so astospread-theame. Accordingito .thezpres- 3 ent invention, the waterproofing coating is rendered highly nre-resistant so that, even when applied to a base sheet of combustible organic fibers, roof-lng can be made which has the high degree of re resistance mentioned above.

The highly re resistant bituminous coating composition of this invention is particularly Well suited for the manufacture of roofngs such as bituminous shingles (individual or strip shingles), cap sheets, base sheets and the like, and, likewise can be used in the manufacture of such products as roll roofing, siding, and in the construction of built-up roofing and the like and generally wherever it is desired to provide roofing comprising a highly fire-resistant bituminous layer.

In our aforesaid application Ser. No. 370,636, we have described and claimed bituminous roofing comprising a Waterproofing layer of bituminous composition which contains intimately commingled with the bitumen component of the composition a filler material of the range 35% to 55 by weight of the bituminous composition that is in the form of finely-divided solid water-insoluble heat-resistant mineral material which passes a 14 mesh testing sieve and over 50% by weight of which -is retained on a 200 mesh testing sieve and which has the special ow resistance characteristics that are described, illustrated and defined in said application.

The special fire-resistant bituminous compositions which are described in our aforesaid application Ser. No. 370,636, instead of burning with melting and flowing of the bitumen in the bituminous coating composition, are characterized by the fact that the ller material contained therein constitutes a skeletal mat that is flowresistant and that when exposed to flame remains in place and keeps the bitumen from bleeding out and by the fact that the bitumen, in becoming carbonized, forms a carbonaceous binder which binds the particles comprising the skeletal mat into a coherent layer that possesses very high heat insulating properties.

The rooiings of the present invention when exposed to fire aord the type of fire-retardant protection that is aiorded by the special fireresistant bituminous compositions that are described in our aforesaid application Ser. No. 370,636, but afford this extremely high re resistance as a result of different formulation that will be described in detail hereinbelow.

The invention herein set forth is based upon our discovery that certain fibers, namely asbestos fibers and cotton fibers of the screen grading defined below, have the capacity when used in minute quantities relative to the other ingredients of the bituminous composition, of greatly increasing the fire resistance of the bituminous Waterproofing coating layer or layers of bituminous roofings, provided the bituminous composition of such layer or layers contains sufcient additional filler material so that the total Weight of the finely-divided solid water-insoluble filler material constitutes at least 35% by weight of the bituminous composition. The quantity of such special fiber may be very small, e. g. 0.1% by weight of the bituminous composition and even less and unless combined with other ller as aforesaid does not by itself have the capacity to appreciably affect the fire resistance of a bitumen with which it is mixed.

The fiber that We have found to have such remarkable effect upon the re resistance of bituminous compositions containing over 35% by weight of nely-divided ller are asbestos iibers and cotton bers that are of the size range passing a .742 inch testing sieve and retained on a No. 6 testing sieve. The asbestos ber referred to is asbestos ber that has been prepared by milling asbestos-bearing rock and separating those fibers which have been completely and thoroughly opened as in the commercial production of asbestos bers for textile fabrication purposes. Such fibers are derivable from asbestiform minerals such as chrysotile, actinolite, amosite and crocidolite.

In determining the screen fractions or gradings of brous or other mineral filler that are referred to herein, 8 inch diameter testing sieves of the W. S. Tyler Company sieve series meeting American Society for Testing Materials Standard E11-39 for Sieves for Testing Purposes have been used. A quantity of ller to be screened ranging from 200 to 300 grams is placed in the uppermost of a series of testing sieves and subjected to suitable agitation as in a standard W. S. Tyler Company Ro-Tap sieve shaking machine for a period of ve minutes in order to separate the original ller roughly into fractions retained on the dierent testing sieves. This operation is repeated if necessary in order to obtain about to 200 grams of the desired screen fraction, which fraction is then individually rescreened for 15 minutes using the Ro-Tap sieve shaking machine or its equivalent in order to remove any fines contained therein. The resulting sieve fraction is material that has passed the coarser screen and is retained on the finer screen. As aforesaid. the ber herein considered passes a testing sieve which has an opening .742 inch and is retained on a No. 6 testing sieve. The intermediate testing sieves in this range are .525 inch; .371 inch; No. 3 testing sieve, and No. 4 testing sieve.

The highly re resistant bituminous compositions of this invention are formulated so that the waterproofing bgtumen in the composition is of the range 20% to 65% by weight of the composition and so that the filler material is of the range 35% to 80% by weight of the composition. Within this range a Wide variety of diluent ller materials may be employed in combination with the special ber above defined. Such diluent filler may be mineral ller or organic filler provided the filler material is of finely-divided solid Water-insoluble particulate form and the filler is composed of material that has a softening point above about 500 F. According to this invention such compositions are rendered highly lire-resistant by the employment of the asbestos fibers or cotton bers passing a .742 inch sieve and 1etained on a No. 6 sieve in an amount that does not exceed about 5% by weight of the composition and that may be as low as 0.1% or less by weight of the composition. While fibers of the character above mentioned are relatively high in price as compared with the other ingredients of bituminous roongs, the fact that they are suitable When employed in relatively small amounts makes the employment of such mineral fibers commercially feasible. Thus, for example, one can, according to this invention, modify a four ton batch of bituminous coating material which has low fire resistance so that the bituminous composition Will afford roofing having very high lire resistance merely by incorporating in the batch of bituminous coating composition only about 5 to 10 pounds of the special fiber above referred to.

In order to afford a better understanding of this invention, it will be described for purposes of exemplication in connection with a typical embodiment. The roong material of this embodiment is composed of a base of strain-resisting roofing felt, a weather surface coating of special bituminous coating composition, a surface layer of mineral granules partially embedded in the surface coating, a thinner layer of the special coating composition on the back of the felt base sheet, and nely-divided dusting material adherent to the back layer of the special bituminous coating composition.

In the exemplary embodiment, the base or foundation sheet is ordinary roong felt made of Vegetable and animal bers, e. g. a roong felt made from organic ber stock weighing about 6 pounds per 100 square feet. 'Ihe felt is impregnated with a suitable impregnating material, e. g. a conventional bituminous roofing saturant having a softening point of about 100 F. to about 170 F. The base sheet as thus composed has little nre resistance and, when exposed to re, is consumed quite readily.

A typical example of the special coating composition is given below:

Per cent Asphalt (softening point 230 F.) 45.0 Slate flour (85% passing a 200 mesh testing sieve) 54.1 Asbestos fiber (passing a .525 inch sieve and retained on a .371 inch testing sieve) .9

It is to be noted that the special fiber only constitutes .9% by weight of the composition. However, notwithstanding the presence in the composition of 54.1% by weight of slate fiour, the coating composition without the very small amount of special fiber tends to iow and burn when exposed to iiame temperature and is devoid of those characteristics which we have found to afford nigh re resistance. But by the incorporation of the very small quantity of the special ber, the character of the Composition upon exposure to flame is greatly modified and high fire resistance is afforded. This effect produced by the small amount of special fiber while seemingly incredible, has been verified by repeated experimental determinations.

In preparing the special bituminous composition, the asphalt is heated to a heat liquefied condition and the above described mineral ller materials are mixed therewith. It is important that the bitumen and nely-divided mineral filler be thoroughly mixed and intimately commingled so that the composition of the coating with respect to the distribution of the ller therein is uniform throughout. The composition should be applied to the base sheet While in a thoroughly mixed condition so that the resulting layer is substantially uniform in consistency and thickness. In this typical embodiment herein described, the vcoating is applied to the felt base sheet at the rate of about i5 pounds per 100 square feet. Before the coating cools to atmospheric temperature, a conventional surfacing material such asV slate granules can be applied to the surface for weather exposure and these granules are partially embedded in the layer of special bituminous composition. The granular surfacing material is preferably non-combustile and, while employed, is not relied upon to impart fire resistance to the roofing. On the opposite side of the roofing material, there may be employed a thin coating of bituminous coating material, e. g.

an asphalt having a softening point of about 200 F. to '240 F., so as to weigh about 5 pounds per 100 square feet, and finely-divided dusting material such as talc or mica dust or similar material may be applied and partially embedded in the back coating. Preferably, for maximum fire resistance, the back coating should be special coating composition embodying our invention.

The roong thus prepared may be packaged in sheet form, or, alternatively may be cut into sections suitable for individual or strip shingles. The roofing weighs about 95 pounds per 100 square feet. Ofthis weight, about 30% by weight is in the form of mineral granules adherent to the weather surface and finely-divided dusting material adherent to the other surface, the balance of the roofing being the felt, the bituminous impregnating material and the bituminous coating composition.

The special bituminous coating composition may advantageously be mixed and applied in the manner mentioned in our said application Ser.. No. 370,636 (Patent No. 2,326,723). As stated in said application, the coating composition may, if desired, in order to increase the resistance of the applied coating to blistering, be applied using the method and apparatus of our Patent No. 2,105,531 and 2,159,587, but this is not essental.

The roong material above described can be made up into suitable rooflngs and roofing structures, description of typical and exemplary roofings and roofing structures being facilitated by reference to the accompanying drawings, wherein Fig. 1 is a plan View of a prepared roong embodying this invention in the form of an individual shingle of simple rectangular shape;

Fig. 2 is a plan view of prepared roofing embodying our invention in the form of an individual shingle of a preferred shape;

Fig. 3 isa plan View of prepared roofing embodying our invention in the form of a shingle strip;

Fig. 4 is a fragmentary cross sectional View on an enlarged scale of prepared roofing embodying our invention;

Fig. 5 is a sectional elevation of an inclined shingle roof embodying our invention without showing the component layers of individual shingles;

Fig. 6 is an enlarged Sectional elevation view of aportion of the roof covering shown in Fig. 5, as installed;

Fig. 7 is similar to Fig. 6 except that the roong is illustrated as it appears after exposure to flame temperature;

Fig. 8 is a plan view of one form of prepared sheet roong embodying our invention adapted to be installed in roll form;

Fig. 9 is a sectional elevation of a portion of an inclined roof deck with the roofing material of Fig. 8 installed thereon, the roong material being shown with exaggerated thickness for clarity;

Fig. 10 is a side elevationI partly in section of the testing device for determining the iiow resistance val-ue ofthe filler contained in the special bituminous-composition;

Fig. 11 is a plan view partly in section of the fire testing device;

Fig. 112 is a front elevation of the test panel 15 with parts thereof broken away; andl Y Fig. 15` is a perspective View of the frame and guard plate used in the test panel assembly.

The prepared roofing material may be cut into individual shingles I Shown in Fig. 1. Preferably the roofing material is cut into individual shingles I0 having the shape shown in Fig. 2 or into strip shingles of the type shown in Fig. 3. Of course, shingles or the like of other shapes may be used in the practice of this invention. In cross section the prepared roofing material appears as in Fig. 4 and comprises a base or foundation sheet I3 of bitumen impregnated roofing felt. Overlying this roofing felt is a coating I4 of special coating composition having adherent to the surface thereof and partially embedded therein the slate granules I2. Adherent to the `back of the roofing material is a layer I5 of the special bituminous coating material in which is embedded finely-divided dusting material 48. Ordinarily some bituminous coating material and dusting material are employed on the back of the roofing material, but these materials are not essential and are sometimes omitted particularly when the roofing material is t-o be used in built-up roong.

In Fig. 5 is shown a typical roofing structure in place on a roof deck comprising boards I6 which serve as a support for the shingles, e. g. strip shingles II or individual shingles I0. The individual shingles may be 16 inches long overall and laid with a 5 inch exposure thereby affording triple coverage over all parts of the roof deck except for a portion of the spaces between adjacent shingles in each course. The component parts of the individual shingles appear in detail in the enlarged fragmentary view shown in Fig. 6.

In the installation of a re-resistant roof covering, the employment of strip shingles of the type shown in Fig. 3 is preferred since the recesses or slots 23 only extend partially into the body of the shingle and since the notches 24 provide recesses of similar depth between abutting pieces of strip shingle, thereby preventing penetration of flame into the body of the roof covering. Individual shingles I0 provided with a notch 25 are preferred for similar reasons.

The preformed roofing can of course be laid with a greater proportion thereof exposed and so that the roof covering will be composed of two layers instead of three. Such a roofing is illustr-ated in Figs. 8 and 9. In Fig. 9 the roofing material is shown as installed on a roof deck with the thickness of the courses exaggerated for clarity. The preformed roofing material consists of a foundation sheet I8 of bituminized roofing material, coated over a part of its width with a coating I9 of the special coating coposition. This material may be made up in rolls 1about 36 inches iwide for example with slightly less than half of the width of the asphalt saturated foundation sheet I8, e. g. 17 inches of the width, coated with the special coating I9 and covered with the mineral granules 20, e. g. slate granules. This type of roofing may be laid on boards 2| of a roof deck using suitable securing means such as nails 26, the slate covered portion being exposed and lthe balance underlying an adjoining sheet as shown in Fig. 9. Where the preformed sheets overlap they are caused to adhere to each other by a bituminous adhesive material 22 which, preferably, has the high re resi-stance of the special coating compositions embodying our invention.

Referring to the above described special re resistant bituminous compzltions and to the roofing and 'roofing structures shown in the accompanying drawings, such roofing has been found to possess extremely high resistance to fire. Thus a roofing structure such as that shown in Fig. 5, namely, comprising three thicknesses of the preformed roofing will withstand the class A re retardant tests prescribed by Underwriters Laboratories, Inc., in their published instructions. As stated in our aforesaid application Ser. No. 370,636, we do not know of any prepared bituminous roong commercially made on a felt base of organic fibers which, irrespective of the weight of the roofing material or the number of layers or plies that are lapplied to the roof deck, will successfully :pass the class A re retardant tests, or iwill even pass the class B fire retardant tests of Underwriters Laboratories, Inc.

When ordinary bituminous prepared roofing, e. g. asphalt shingles applied so as to provide triple layer coverage of the deck, is subjected to the class A burning brand test, for example, the coating material when exposed lto the brand melts and as a mass starts running down the surface of the roof. The melted asphalt also starts to burn and the burning asphalt in running down the roof spreads the re. The coating material that runs down the roof leaves the bituminous organic felt base exposed which, being readily combustible, starts burning so that the fire goes through the roofing quite readily and ignites the combustible roof 'deck in ra relatively short time.

By way of contrast our improved roofing which contains the special re-resistant bituminous coating layer -behaves very differently when subjected to fire as in the burning brand test. The behavior of the roofing material as applied in three layers to a roof deck, e. g. as shown in Figs. 5 and 6, is indicated roughly in Fig. 7. During exposure to the flame the speci-al bituminous composition instead of flowing and running, remains in place -due to .the stabilizing action of the filler materials contained in the bituminous composition. As aforesaid, the fine filler such as slate flour has little or no stabilizing action, but we have found that when such filler material is combined with the selected screen gradings of the special fiber the composition lbecomes stabilized and highly resistant to flowing and to combustion. Moreover, during the exposure t0 flame small bubbles 27 are formed which tend to exipand the coating composition and augment its leffectiveness as a heat insulating layer.

In the roof covering as a .whole as illustrated in Fig. 7 the upper layer of special bituminous composition has become expanded somewhat and has become somewhat irregular, but the coherent porous mat-like mass has remained and acts as a protective barrier against the flame. The uppermost layer E3 of felt may be carbonized and to a considerable degree may have disappeared leaving air pockets 28 together with` some residual carbonized material. The intermedi-ate layer I4 of special bituminous composition is also eX- panded, but remains in place as a protective heat insulating layer. The intermediate layer of felt is charred, but is better preserved than the uppermost layer of felt. The bottom layer of the special bituminous composition is less severely carbonized Ithan the upper layer and likewise is considerably expanded. The bottom layer of felt is fairly well preserved and the upderlying Iboard I6, if charred at all, has not Ibecome ignited. The 4backing layers I5, when composed of the special bituminous composition, likewise augment the heat insulating effect of the roof deck covering, but it is not essential that these layers I be composed of the special bituminous composition of this invention in order for the roof covering to pass the class A iire retardant test of Underwriters Laboratories, Inc. In making the class A burning brand test of Underwriters Laboratories, Inc., it usually takes the burning brand about 30 to 45 minutes to burn out. During this time the upper surface of the uppermost layer I4 may become red hot, but the heat insulation effect of the carbonized residues of the layer IA is so great that the board I6 does not become ignited and may not even appear scorched.

When the special bituminous composition of this invention is exposed to name, the effect of the flame is conned to the area immediately beneath and closely adjacent to the area of direct exposure to ilame and when the ame becomes extinguished all charring of the roong soon ceases and the roong cools down.

A roong such as that shown in Figs. 8 and 9 which provides double coverage will successfully pass the class B fire retardant tests of Underwriters Laboratories, Inc., when the special bituminous composition is made according to this invention.

The high re resistance of the special bituminous coating composition is due to a combination of factors. The effect of the relatively small amount of special fiber in stabilizing the entire bituminous mass when it is exposed to flame has been mentioned above. of the slate flour as diluent ller is essential, for if the diluent filler were omitted the small amount of special fiber by itself would have no appreciable effect in stabilizing the bitumen. On the other hand the slate flour in the amount used has virtually no eiect in stabilizing the bitumen. However. when these filler materials are employed in combination, the very small amount of the special ber coacts with the balance of filler in the composition so that the total fiber in the composition -becomes converted to a stable skeletal mat within the waterproofing bitumen. The bitumen that is present in the bituminous composition likewise cooperates with the skeletal mat of fiber and other filler for upon exposure of the composition to flame it tends to carbonize without excessive combustion to form a cementitious binder for the skeletal mat of ller material so that the filler is held in place as a coherent layer or mat that not only resists combustion but also has extremely high heat insulating eiectiveness.

As stated in our aforesaid application Ser. No. 370,636. the property of a i'lller or filler mixture of imparting flow resistance to a bituminous composition, when the bituminous composition containing it is exposed to ame temperature is a definite property and is a property that is capable of accurate measurement. However, since this property of ller materials and its 'use in imparting fire resistance to bituminous compositions were not known prior to our invention as described in our said application Ser. No. 370,636, we found it necessary to devise a test apparatus and procedure whereby this property can be accurately measured. The test consists in directing a flame against an inclined specimen of roofing. that carries a coating composition consisting of bitumen and the iiller or ller mixture under precisely controlled conditions determined by the construction and operation of the testing appara- However, the presence tus. This test and test procedure are described below, reference being made to Figs. 10 to 15 of the accompanying drawings.

Samples of material to be tested are made by applying bituminous coating material to an asphalt saturated organic liber felt base sheet so that the coating weighs 25 pounds i2 pounds per 100 square feet. No granular material or the like is applied to the surface of the coating. The asphalt saturated felt base sheet weighs about 30 pounds per 100 square feet and is saturated to the extent of about 175% by weight with asphalt having a softening point of about 150 F. The bituminous coating material is applied by coating the felt in lthe machine direction of the sheet and the felt is applied to the test deck so that the machine direction of the sheet is parallel to the direction of flame travel.

The test is made in the wind tunnel 53 having a fan 54 at one end anda stack 55 at the other end. The tunnel is made of 1A; inch thickness asbestoscement lumber and has two windows 56 and 51 therein which can be opened and closed by any suitable means (not shown).

Within the tunnel are the burner and testing deck which are located between two shields 58 and 58 of the asbestos-cement lumber spaced 121/4 inches apart, and which are rigidly mounted on an asbestos-cement slab 43. The inclined test deck is indicated generally by the reference character 59 and comprises a lower iron-framelike member 60 having 1/4 inch pegs 6i projecting from the face adjacent the upper and lower margins. Between the pegs strips 62 of combustible material 1% x 12 x 1A inches are placed. This combustible material is what is known as Masonite Quarterboard and is selected instead of wood because it can be obtained with greater uniformity than can wood. Masonite Quarterboard is made from wood ber by compression of the fiber of a berized mass in the presence of a binder until it has a density of about 36 pounds per cubic foot. The four center boards are dried at 180 F. in a steam oven for at least 7 days. Two full plies 12 x 12 inches of the roong 69 to be tested and one half-ply 12 x 6 inches are placed on the combustible deck followed by an L-shaped guard plate 63 which guards the bottom edge of the roong and of the Masonite. The assembly is held down by an iron frame 54 open at the bottom and held in place by thumb screws 65.

After the test deck has been assembled it is placed on the inclined support 66 which has an opening in the back underneath the combustible material62 and which has side anges 66 to protect each side of the test panel. The support 66 comprises a baiile 61 to prevent the flame from licking around behind the test deck. The support which is made of iron is mounted on the asbestos-cement slab 43 which measures 12 X 40 X 1 inches. The parts for carrying the test deck are also made of iron. An iron bar 68, 12 x 1 x 1/4 inches, is placed across the top edge of the deck to protect the combustible material at this point.

In front of the test deck is the burner l0 comprising an iron pipe having an inside diameter of .472 inch and an outside diameter of .675 inch, with 17 holes 0.078 inch in diameter and 1/2 inch apart disposed at an angle that is parallel with the plane of the test deck. The burner has one inlet il controlled by a valve 'i2 and another inlet 13 controlled by a valve 15.

The dimensions of different parts of the testing apparatus shown on the drawings as used 4by us are as follows:

Inches Inches a 24 0 8 b 38 p 2 b 6 q 3A c 181/2 r 1 d 72 s 12 e 161/2 t 7 f 10 u 101/2 g 12% v 12 h 38 w 12 z 64 :c 1 y 32 y 12 7c 24 y' 1 Z 24 z 6 m 40 aa 12 11. 27 bb 1 In carrying out the test the apparatus is rst assembled and the burner is lighted, the valve 12 being open and adjusted until a pilot flame is produced that is about 1/2 inch in length when the fan is operating. The windows 56 and 51 are then closed and the room in which the apparatus is placed is arranged so that there will be relative constant conditions during the test. The temperature and relative humidity of the room should be approximately 80 F. and 40%, respectively. The fan should generate a wind velocity of about 150-155 feet per minute at the Iportion of the deck exposed to the flame. The valve 'I5 is then opened until a flame about 8 to 9 inches long is produced having a temperature of about 1325-1370 F. When the valve15 is opened to increase the flame a timing device is started.

During the test the upper surface of the test deck can be observed as well as the back composed of combustible Masonite strips. During the test the behavior of the coating material can be noted including possible exposure and combustion of the felt base sheet, the flowing of coating material down the roof deck, etc. When one or more of the Masonite strips of the test deck catch iire and begin to burn the test is concluded. If the Masonite merely carbonizes without breaking into ame the end point has not yet been reached.

During the progress of the above described test the heat of the flame tends to soften the bitumen in the bituminous composition and, in the case of ordinary bituminous coating composition, the composition melts and to large extent flows ofi leaving the felt exposed so that it catches fire and burns through with the result that the Masonite boards soon become ignited. When, however, the bituminos composition of this invention is em.- ployed. the mineral ller forms a stable skeletal mat within the bitumen and the bitumen tends to remain in place, and the residual material to the extent that it does remain in place protects the felt and retards the ignition of the Masonite boards. The time in minutes required to ignite the Masonite boards is the ilow resistance value of the filler or iiller mixture being tested, and in our aforesaid application Ser. No. '370.636 we stated that the filler material to be suitable should have a ilow resistance value of atleast 40 minutes when subjected to the above described test. This is to be contrasted with 18 minutes for the felt without any coating at all applied thereto and with 13 minutes for the felt coating with the asphalt unmixed with any ller, and with a period of 17 minutes for the asphalt containing 35% of slate iiour and no other iiller. When a illler material, or a particular grade of iiller materia1 is stated herein and in the claims to have a iiow resistance value of 40 minutes or greater than, or less than, 40 minutes, the ow resistance value as measured by the above described testing Y be.

apparatus and procedure is intended.

In our aforesaid application Ser. N o. `370,636 the iiow resistance test is described as carried out with the ller consituting by weight of the bituminous composition, the balance of the bituminous composition consisting of roofing asphalt having a softening point of about 230 F. However, for the purpose of defining the re resistant roongs of the present invention, the flow resistance value, unless otherwise specied is the flow resistance value of the iiller mixture in Whatever amount it is used in the bituminous composition and as incorporated with whatever the bitumen component of the composition may Referring to the above mentioned example of the practice of this invention, if slate our is substituted for the .5% of special asbestos fiber, so that the composition consists of 55% by weight of slate flour and 45% by weight of asphalt having a softening point of 230% F., the flow resistance value of the slate flour is only about 32 minutes and the rooiing is incapable of attaining any rating according to the re retardant tests of Underwriters Laboratories, Inc., higher than a class C rating, which is the rating that is assigned to ordinary commercial bituminous roofings. However, when the .9% of special fiber is incorporated in the bituminous composition the ilow resistance value is raised to 58 minutes, and the roongs carrying Such coating will meet the requirements of the higher ratings under the tests prescribed by Underwriters Laboratories, Inc., as has been mentioned hereinabove.

Within the range passing a .742 inch testing sieve and retained on a No. 6 testing sieve, the different intermediate screen gradings differ somewhat from each other in their eilectiveness. This may be illustrated in the following table which shows the eiectiveness of the different screen gradings of chrysotile asbestos ber in a flow resistance value of about 40 minutes.

composition consisting of asphalt having a softening point of 230 F., slate Hour, 85% of which passes a 200 mesh testing sieve, and the screen y fractions of the special chrysotile asbestos ber,

7 screen grading passing a .742 inch testing sieve and retained on a .525 inch testing sieve is indicated as (-.742 inch-#.525 inch). The screen grading passing a N o. 3 testing sieve and retained l on a No. 4 testing sieve is indicated as (-3+4).

Other gradings are indicated similarly.

Total Filler Screen Grading 55% by weight 35% hy weight of composition of composition (-.742 inch-i-.525 inch) 05 3 (-.525 inch-P371 nch). 1 8 (-.371 inch-F3) 2 1.0 (-3-I-4) .25 1.2

The foregoing is illustrative of the varying effectiveness of the different screen gradings of the special asbestos ber when a typical thoroughlyo-penedV grade :of chrysotile4 asbestos ber is fused.

The -other ber that-is Ymentioned hereinabove is cottonliber'of the screen gradings `above': mentioned. The diierentscreengradings'of cotton fiber: areslight1y` less-efectivethan the corresponding screen gradings of asbestosber. One can of course utilizea mixtureof theasbestos ber and cottonfber of the screeny gradings mentioned.

While the special asbestos and cotton bers have the remarkable stabilizing. actionthatihas been pointed out above, it is important that these fibers be'employed in the veryfsmalloua'ntities that have been mentioned. If attemptis `made to incorporate inthe re resistant bituminous composition more than about-5% by weight of the-composition'of these special fibers, the fibers tend to form into clotsor clumps-that are undesirable. These clots or clumps during appli cation of the coating tend to be dragged'along leaving areas or zones that are virtually unprotected both from the point of View of resistance to weather and from the point of view of resistance to re. Moreover, the presence of more than a small amount ofspecial fiber ktends to -impair the adhesion of the coating to the underlyingfelt when the coating is subjected to the heat of a ame. However, when these special bers are'employedin the Vvery small quantities above mentioned ranging from an amount that is merely a fractional percent of the composition up to about 5% -by weight of the composition, the special bers can lbe successfully incorporated. in a bituminous composition that when heat plasticized-is spreadable to form a layer of uniform is employed in the bituminous composition there is a -Wide selection. There are a number of heat resistantimineral fillers which are suitable other than slate flour, e. g. limestone dust, silica flour, clay, v talc, fly ash, hydrated Portland cement,

dead-burned calcium sulphate, precipitated cal cium silicate hydrate andthe like. Most fillers of such characterare of such state of .subdivision that about 90% by weight thereof-will vpass a 100 mesh testing sieve.

Fillers such as asbestiform mineral ber which is of the type referred toas dustand wloiclfiis discarded in enormous quantities on the dumps as a'waste by-product of the milling of thecommercial grades of asbestos fiber may be used` Such asbestos dust, as well as other nely-divided iibrous minerals such as disintegrated asbestoscement scrap, disintegrated ber-bearing serpentine rock, finelydivided mineral wool and iinely-divided glass fibers have -been disclosed in our application Ser. No. 370,636 as providing highly iire resistant bituminous coatings if used inthe quantities and state of 'subdivision therein specified. One can advantageously, according to the present invention, employ the special bers passing a .742 inch testing sieve and retained on a No.V 6 testing sieve in conjunction with the more finely-divided ibrous minerals and with or without non-brous' mineral fillers for by so doing theV fire resistance of the bituminous composition is increased, but itis apparent 'thatlthe quantitw of: thespeciafl berwvhich. is employed inv -thev practicer ofA Miei-inventions canbe'fieduced still furtheifto extremely minutev quantities as compared with fthe :bituminouscomposition as a Whole in comparison''withthe amount `required toV achieve-arflowfresistance value of 40 minutes when a llerisuc-hias slate our is employed that by. itself haslittle effectiveness;

In addition'1to-.mineralfillers, organic .iiller 'material @maybe em-ployed although :it is,` usually advantageous to veinlploy a-v heat-resistant mineral filler iny an amounty such-that the ratio' of the percent ybyfweight-'oa heat-resistant mineral filler in -the ybituminouscomposition to theV percentzby weight of .Waterproongzbitumen inthe rbituminouscom'position is-at least 1 to'3 and even more desirably at llleast'l 4tol 2. By heat resistant any material I that.. retains-`V stru'otural r integrity when acoatingicomposition containing it `is exposed to flame temperaturezisi intended` and any1 material such'as clirysotile` asbestos, kaolin clay; or the like thatLconta'ins-wateihof constitutionliberata'bie at or below'lani-e temperaturesis` regarded Vas heat resistanty.

Among-- thei organic l-le'rs are f fibrous fill-ers which may-be anima-1,1 vegetable or? synthetic, e; g. fibrous fillers :suchiasgrades of cotton fiber that areshOrter' thanrthe special grades of 2 cotton above mentioned,- wool; sawdust, debrated wood,

I paper fibers,(sulphiteforkraft), regenerated =ce1 lu'losel (rayon.) g cellulose: acetate# and the-vV like; Such ,-ibe-rs.n themselves have: a' stabilizing action on.- the. bitumen of f a bituminous: composition, but-the employment :of the-'fspeci'aliibersof this invention serves to 'improve upon the fire-re# sstance of the bitunfiifnmis` compositionasv a Whole. l

Non--brousr-orga'nic--vllerfmaterials may likewise-- be. erri-ployed4 such as finely-divided.` cork, coal, cokefA groundihardrubber', ground synthetic resins,` (suc-h as--A phenol-aldehyde: resins; lignin resinsand the like),- pyrobitumens, Aand the like.

More-.generally any1 neiyedivided -watereinsoluble fillerorliler: mixturel maybe employed provided thediller: material .has a softeningv point above. about 5009 F. andfpreferably above about 700`F. `and provided-theller orfllermixtures can befincorporated''in' a bituminous composition that iis-spreadable 4a heat plasticized `Vcondition when the diluent filler'pluswfthe4 special yber that is employedIaccordingf-to this invention provides a total ififller= content' constituting '35% or= more by weight sofiA the` bituminous composition. In determining-,the softening point of the ller material thestandardcube-in-air softening point test is vreferred to.`

In formulatng the bituminous. composition` it is;desirab1e,.-.however that atleast about vhalf by.V weight of -vthe: ller' material lbe suiciently finely divided .to pass-al00-mesh testing sieve andv whenptheutotal .nllen content is` of the yrange 55% to; 80% -byfweight of the bituminous composition it .is-desirab1e tha/tat leasttwo-thirds by weight .ofthe fillenmaterialfpass a. `mesh testingsie've.` It'is alsodesirable Ato .avoid the presence of'non-fibrous filler material retained on a 14mesh`4 tstingsieve and any excessive amount of'b'ersretainedona 14 mesh testing sieve is undesirable dueto theffactthatsuch filler material detracts from the'spreadability, of the coinposition; Accordingly; itis iusuanydesirab'le. that the1amount'of"11ler materialretained Yon aile meshLtesting-sivezbe less than about10`%"by weight of thettallle material "inthe b'itumi nous'composition;

With regard to the waterproofing bitumen that is employed in the fire resistant bituminous composition, it is usually preferable in the manufacture of shingles or the like to employ an asphalt having a softening point of about 200 F. to 250 F., although a somewhat broader range is permissible, namely, asphalts having a softening point of about 160 F. to about 275 F. For more flexible products such as roll roofing, an asphalt having a softening point of below 160 F. may be used, and roongs of satisfactory re resistance can be produced utilizing asphalt having a softening point above 80 F., although it is usually preferable, even in the case of roll roongs and the like, to utilize an asphalt having a softening point above 120 F. The softening point of the waterproong bitumen is determined by the standard ball and ring test. In addition to asphalts derived from Mid-Continent crudes, other asphalts are suitable such as asphalts derived from Mexican, Venezuelan and Colombian crudes. Other bitumens such as pitches, coal tar and the like may be used in the practice of this invention. Moreover, any modifier, e. g. of a resinous or oily character, that may be mixed and blended with the bitumen is to be regarded as part of the bitumen content of the composition.

When reference is made herein to Waterproofing bitumen this term is used in reference to asphalt, tar, pitch and the like having a softening point of the range 80 F. to 275 F. and unmixed with filler. If any bituminous material comprising bitumen having a softening point above 500 F. such as pyrobitumens, e. g. grahamite, Wurtzilite and the like, is employed or if a very highly oxidized asphalt is employed in a powdered state, such bituminous material is regarded as part of the filler and not part of the waterproofing bitumen. When reference is made herein to a bituminous material, or a bituminous coating or a bituminous layer, reference is made to a material, composition, coating or layer com- -prising bitumen either with or without filler.

In the foregoing example of the practice of this invention the special bituminous coating composition was applied in layer form at the rate of 45 pounds per 100 square feet of the roofing. It is usually desirable to apply the special bituminous coating material to the weather exposed side of the base sheet so that the layer will weigh at least pounds per 100 square feet, the range ordinarily being from about to about 60 pounds per 100 square feet, although about to about 50 pounds per 100 square feet is usually preferable. In the foregoing example wherein the special bituminous coating material contained substantially 50% by weight of filler and the coating was applied at the rate of 45 pounds per 100 square feet, the amount of iiller in the coating composition constituted about 22.5 pounds per 100 square feet of the roofing material. For prepared roofing materials it is usually desirable that the roofing material contain in one or more layers such as a surface layer or backing layer, sufcient of the special bituminous composition so that the roofing material will contain at least 7 and preferably about 14 pounds per 100 square feet of the filler material. By varying the number and thickness of the layers of special bituminous coating composition of this invention, varying degrees of fire-retardant effectiveness can be attained. The special bituminous composition of this invention is especially effective when .it is disposed in a roofing so as to occur in a plurality of layers separated by felt or other sheet material, for example, as shown in Figs. 5, 6 and 9. In such plural layer construction it is desirable that the total filler constitute at least about 15 pounds per 100 square feet of the roof covering and preferably about 42 pounds per 100 square feet of the roof covering. It is also desirable that each of at least two layers of the special bituminous composition contain at least 7 pounds per 100 square feet and preferably at least about 14 pounds per 100 square feet of the `roof covering cf the finely-divided solid waterinsoluble ller.

While embodiments of this invention have been shown in the form of preformed roofing materials such as shingles and roll roofing, it is apparent that the special bituminous composition of this invention may be employed in the manufacture of roof coverings installed on the job, such as built-up roongs, certain types of which are exemplied in our aforesaid application Ser. No. 370,636.

It is one of the advantages of this invention that the new roofing herein defined possesses high re resistance without sacrifice of other properties required for a roofing and without substantial increase in cost compared with conventional roofings heretofore manufactured. The new roofing of this invention has very good weathering characteristics and is rough and pliable. Thus a typical preformed roofing material such as a shingle can be bent 180 of arc in two seconds around a 4 centimeter mandrel with the fire-resistant special coating composition on the outside without cracking the coating through to the felt base, the test being made at 77 F. It is desirable that a roofing having a bituminous waterproong coating be sufficiently pliable to bent bent 180 of arc in two secc-nds about a mandrel 10 centimeters in diameter at 77 F. with the coating on the outside without cracking the coating through to the base on which it is applied, and any such coating or layer is referred to herein as pliable at ordinary temperatures.

While ielt sheet materiel has been mentioned r hereinabove as the strain resisting shect-like clement of roongs and roof coverings embodying this invention, it is apparent that any other suitable sheet-like base material, either fibrous or non-fibrous. either foraminous or non-foraminous, and either deformed or non-deformed that is adapted to afford the desired strength char acteristics may be employed. Thus fabrics other than felt may be employed such as woven fabrics or fabrics of unspun bonded fibers. rIhe base sheet may, if desired, be saturated with a bituminous or other waterproofing material or may be dry. Sheet material such as a composition board or insulation material may be employed. Plain or corrugated or indented sheet metal may be employed as the base sheet. Ordinary roofing felt made of organic fibers is, however, the most inexpensive sheet material, and, notwithstanding the combustibility of such sheet material, roofings comprising it can, according to this invention, be made highly fire resistant. If desired, non-combustible fibers can be incorporated in the felt or other brous base sheet to augment the fire resistance of the roofing.

It is apparent that one can by the employment of this invention provide highly fire resistant bituminous compositions that have a flew resistance value of at least 40 minutes and preferably a flow resistance value of at least 80 minutes, by the expedient of incorporating in a bituminous composition containing finely-divided solid waterinsoluble mineral filler which has a softening point above 500"F. and which is ofthe range-35% to '80% by AWeight ofthe composition, asm-all amount of the special: asbestos liber or cotton` fiber or any vmixture thereof in amounts which are 4not greater`v than 5% by -weight ofthe bituminousl composition and which may be below va tenth of one percent by-Weight ofthe bituminous composition. The amount that 'is used will vary somewhat depending upon the percent by weight of bitumen inthe composition, and the presence or absence of other brousmineral inthe composition.

While this invention has been described in connectionwith certaintypicalexamples of. the practice thereof, it is toobe yunderstood that' this has been done for purposesof exemplication. Accordingly the scope'of4 this invention is. to be governednby the language of thefollowing claims construed in the. light o the foregoing description. of.. our invention.

We claim:

1.. A roong having high resistance to re oomprising sheet-likev base` material and a layer of thermoplastic bituminous composition carried by said sheet-like base material, said bituminous composition containing waterprooing bitumen having a softening point above 30 F. and not above 275 F. and of the range 26%- to 65% by Weight of said bituminous. composition, and said bituminous composition containing intimately commingled and distributed uniformly throughn out finely-divided solid water-insoluble nller having a softening point above .500 F. and of the range 35% to 80% by weightof said bituminous composition, said filler consisting in major proportion by Weight of particles passingY a 100 mesh testing sieve and comprising less than 10% by Weight of the total filler of particles retained on a 14 mesh testing sieve, said filler comprising fiber which is selected from the group consisting of asbestos fiber and cotton fiber and mixtures of said fibers, which passes a .742 inch testing sieve and is retained on a No. 6 testing sieve and which is present in appreciable amounts constituting less than 5% AbyWeig-ht of said bituminous composition, and said bituminous composition when heat plasticized being spreadable to form a layer of uniform thickness and uniform consistency and providing a pliable Weather resistant layer of the hot-Spread coating type integrally bonded with said sheet-like base material.

2. A roofing according to claim l wherein said ller passing a .742 inch testing sieve and retained on a No. 6 testing sieve consists predominantly of asbestos liber.

3. A roofing having high resistance to iire comprising sheet-like base material and carried by said sheet-like base material a layer of thermoplastic bituminous composition, said bituminous composition containing Waterproofing bitumen having a softening point above 80 Rand not above 275 F. and of the range 45% to 65% by Weight of said composition, said bituminous composition containing intimately commingled and distributed uniformly throughout finely-divided solid Water-insoluble filler having a softening point above 500 F. and of the range 35% to 55% by weight of said bituminous composition, said ller consisting in major proportion by weight of particles passing a 100 mesh testing sieve and comprising less than 10% by Weight of the total iiller of particles retained on a 14 mesh testing sieve, said filler comprising fiber which is selected from the group consisting of asbestos ber and 18 cotton liber and-mixtures of-said fibers, which passes a .742 inch testing sieve and is retained on a No. 6y testing sieve and which is present in appreciable amounts constituting lessv than 5% by weight of said bituminous composition, said ller including saidr` fiber contained in said: bituminousy composition-asapplied to said sheet-like base material'having a flowresistance value of at least 40 minutes, and said bituminous composition when heat plasticized being spreadable to form a layer of uniform thickness and uniform consistency and providing-a pliable Weather resistant layer of the hot-spread coating type integrally bonded with said sheet-like base material.

A roofing according toclaimv 3 wherein' said finely-divided solid Water-insoluble filler comrises heat resistant mineral filler the ratio of the percent by weight of which to the percent by weight of/waterproofing bitumen in said bituminous composition is atleast 1 to 3.

5. A roofing according to claim 3 wherein said fiber consists essentially of asbestor fiber and said finely-divided solid Water-insoluble Vller consists essentially of heat resistant mineral ller.

6. A roonng having high lire resistance oomprising sheet-like base material and carried by said sheet-like base material, a layer of thermoplastic bituminous composition, said bituminous composition containing waterproofing bitumen having a softening point above F. and not above 275 i1". and of the range 20% to 45% by weight of said composition, said bituminous composition containing intimately commingledand distributed uniformly throughoutl iinely-divided solid Water-insoluble filler having a softening point above 550 and of the range 55% to 80% by Weight of said bituminous composition, at least about two-thirds by Weight of said ller passing a mesh testing sieve and less than 10% by weight of said filler being retained on a l4-mesh testing sieve, said nller comprising ber which is selected `from the group consisting of asbestos liber and cotton 4liber and. mixtures of said fibers, which passes a .742 inchv testing sieve and is retained on a No. 6 testing sieve and which is present in appreciable amount constituting less than 51%V by Weight of saidv bituminous composition, said bituminous composition when heat plasticized being spread'able to form a layer of uniform thickness and uniform consistency, said ller including said fiber contained in said bituminous composition as appliedv to said sheet-like base material having a flow resistance value of at least 40 minutes, and said bituminous composition providing a` pliable weather resistant layer of the hot-spread coating type integrally bonded With said sheet-like base material.

7. A highly fire resistant prepared roong material comprising sheet-like base material-and a layer of thermoplastic bituminous composition carried by said sheet-like basematerial, said bituminous composition containing Waterprooiing bitumen having a softening point above F. and not above 275 F. and of the range 20% to by Weight of said composition, said composition containing intimately commingled and distributed uniformly throughout iinely-divided solid Water-insoluble ller having a softening point above 505 F. and of the range 35% to 80% by Weight of said bituminous composition, said filler consisting in major proportion by Weight of particles passing a 100 mesh testing sieve and comprising less than 10% by weight of the total filler of particles retained on a 14 mesh testing 75 sieve, said filler comprising liber which is selected from the group consisting of asbestos fiber and cotton ber and mixtures of said fibers, which passes a .742 inch testing sieve and is retained on a No. 6 testing sieve and which is present in appreciable amount constituting less than by weight of said bituminous composition, said iiller including said liber contained in said bituminous composition as applied to said sheetlike base material having a ow resistance value of at least 40 minutes, said composition being spreadable in a heat plasticized state to form a layer of uniform thickness and consistency, said layer being a weather resistant layer of the hotspread coating type integrally bonded with said sheet-like base material and being applied at the rate of about 20 pounds to about 60 pounds per 100 square feet of said roofing material, and said roong material being pliable at 77 F.

8. A highly lire resistant prepared roong according to claim 7 wherein said ller comprises heat resistant mineral ller the ratio of the percent by weight of which to the percent by weight of waterproofing bitumen in said bituminous composition is at least-r1 to 3.

9. A highly re resistant prepared roong material according to claim 7 wherein said waterproofing bitumen is of the range 20% to 45% by weight of said bituminous composition, said iinely-divided solid water-insoluble iiller is of the range 55% to 80% oy weight of said bituminous composition and at least two-thirds by weight of said finely-divided solid water-insoluble filler passes a 100 mesh testing sieve, and wherein said filler comprises heat resistant mineral ller the ratio of the percent by weight of which to the percent by weight of waterproofing bitumen in said bituminous composition is at least 1 to 2.

l0. A highly le resistant prepared roong material according to claim 7 wherein said fiber consists essentially of asbestos ber.

11. A roof covering having high resistance to re, comprising sheet-like base material and a plurality of layers of thermoplastic bituminous composition carried by said sheet-like base material, said bituminous composition containing waterprooiing bitumen having a softening point above 120 F. and not above 275 F. and of the range 20% to 65% by Weight of said composition, and said bituminous composition containing intimately commingled and distributed uniformly throughout finely-divided solid water-insoluble filler of the range 35% to 80% by Weight of said bituminous composition and having a softening point above 500 F., said iiller consisting in major proportion by weight of particles passing a 100 mesh testing sieve and comprising less than 10% by weight of the total ller of particles retained on a 14 mesh testing sieve, said filler comprising fiber which is selected from the group consisting or" asbestos fiber and cotton fiber and mixtures of said bers, which passes a .742 inch testing sieve and is retained on a No. 6 testing sieve and which is present in an appreciable amount constituting less than 5% by weight of said bituminous composition, said iiller including said ber contained in said bituminous composition as applied to said sheet-like base material having a flow resistance value of at least 40 minutes, said ller including said ber constituting at least l5 pounds per 100 square feet of said roof covering with at least 7 pounds per 100 square feet contained in each of at least two layers of said coating composition, and said bituminous composition when heat plasticized being spreadable to form a layer of uniform thickness and uniform consistency and providing pliable weather resistant layers of the hot-spread coating type integrally bonded with said sheet-like base material.

12. A roof covering according to claim 11 wherein one of said layers of said bituminous composition is on the weather side of said roof covering and is applied at the rate of at least 30 pounds per 100 square feet, and wherein said nely-divided solid Water-insoluble filler constitutes at least 42 pounds per 100 square feet of said roof covering with at least about 14 pounds per 100 square feet contained in each of at least two of said layers.

13. A roofing having high resistance to re according to claim 1 wherein said sheet-like base material is in the form of brous sheet material.

14. A highly iire resistant prepared roong material according to claim 7 wherein said sheetlike base material consists essentially of felted ber sheet material impregnated with a bituminous waterproong material and wherein surfacing granules are embedded in the normally weather exposed surface of said layer of thermoplastic bituminous composition that is integrally bonded with said sheet-like base material.

HAROLD W. GREIDER. GEORGE ARTHUR FASOLD.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 732,663 Stempel June 30, 1903 1,751,690 Faben Mar. 25, 1930 1,895,320 Gravell Jan. 24, 1933 1,949,229 Yeager Feb. 27, 1934 2,157,696 Greider May 9, 1939 2,158,772 Beckwith May 16, 1939 2,178,770 Zaisser Nov. 7, 1939 2,255,826 Speen Sept. 16, 1941 2,317,209 McCluer Apr. 20, 1943 2,326,723 Fasold et al Aug. 10, 1943 2,354,593 Greider et al. July 25, 1944 OTHER REFERENCES Petroleum Zeitschrii, vol. XXIX, Nr. 45 (1933), pp. l to 12. 

